Submitted on June 6, 2007
Accepted on October 8, 2007
Regulation of PDH in human arm and leg muscles at rest and during intense exercise
Kristian Kiilerich1*, Jesper b birk2, Rasmus Damsgaard3, Jorgen F.P. Wojtaszewski4, and henriette pilegaard5
1 Molecular Biology, University of Copenhagen, Copenhagen, Denmark; , Denmark
2 Exercise and Sport Sciences, University of Copenhagen, United States
3 Bispebjerg Hospial, Denmark; , Denmark
4 Molecular Biology, University of Copenhagen, Denmark; Human Physiology, University of Copenhagen, Denmark; , United States
5 Molecular Biology, University of Copenhagen, Denmark; , Denmark
* To whom correspondence should be addressed. E-mail: kkiilerich{at}aki.ku.dk.
To test the hypothesis that pyruvate dehydrogenase (PDH) is differentially regulated in specific human muscles, regulation of PDH was examined in triceps, deltoid and vastus lateralis at rest and during intense exercise. To elicit considerable glycogen use, subjects performed 30 min exhaustive arm cycling on two occasions, and leg cycling exercise on a third day. Muscle biopsies were obtained from deltoid or triceps on the arm exercise days and from vastus lateralis on the leg cycling day. Resting PDH protein content and phosphorylation on PDH-E1
site 1 and 2 were higher (P
0.05) in vastus lateralis than in triceps and deltoid as was the activity of oxidative enzymes. Net muscle glycogen utilization was similar in vastus lateralis and triceps (
50%), but less in deltoid (likely reflecting less recruitment of deltoid), while muscle lactate accumulation was 55% higher (P0.05) in triceps than vastus lateralis. Exercise induced dephosphorylation (P0.05) of both PDH-E1 site 1 and 2 in all three muscles, but more pronounced at PDH-E1 site 1 in triceps than in vastus lateralis (P0.05). The increase in PDHa activity after 10 min of exercise was more marked in vastus lateralis (246%) than triceps (160%), but when related to total PDH-E1 protein content no difference was evident. In conclusion, PDH protein content seems to be related to metabolic enzyme profile, rather than myosin heavy chain composition, and less PDH capacity in triceps is a likely contributing factor to higher lactate accumulation in triceps than vastus lateralis.
